To take an opportunity to do something when the time and conditions are near perfect or available.
, when farmers gather the long grass growth of summer to dry it to produce hay
as winter feed for animals; The best time to cut and dry the hay is during sunny days.
A:"There's a sale at K-mart this week - You wanna see if the have something for your sister's birthday?"
B:" Sure - Might as well make hay while the sun shines, and get her something at cut price!"
To take advantage of a brief opportunity while it is still there. To not waste time.
The saying comes from farming communities. There would often be only a short time in which the hay would be ready to cut- reap too soon, and the hay would be too green. Reap too late, and you run the risk of rain ruining it all. Still very good advice.
I just got a good job for the summer- I don't know if I'll have one this fall, but I'll make hay while the sun shines and save up for the winter.
To do something while you have the time to do it.
I had some free time in class, so I made hay while the sun shone and did the extra assignment.